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KEY MESSAGES

- Risk for isolated severe storms tomorrow (Friday), mainly across northeastern WY into far western SD. Main hazards will be large hail (1+" in diameter) and damaging wind gusts (60+ mph)

- Risk for scattered severe storms across northwestern SD on Saturday.

- Near the middle of next week through the second week of July, temperatures will be well above normal. Confidence in daily high temperatures in the 90s to low 100s is increasing. The CPC has much of the CWA under a risk of extreme heat.

UPDATE

Issued at 1008 PM MDT Thu Jun 25 2026

No big changes were made to the short term forecast. Main changes were to tighten up the diminishing PoPS tonight in an attempt to match what was happening on satellite and radar. Quiet skies for most of Friday but as a deepening low pressure slides in from the west, that will increase the thunderstorms chances. Any storms that are able to get going look to begin in NE WY and track northeast into western SD. Main concerns are built around the idea that storms will be more elevated, so strong wind gusts with a secondary concern of hail.

The bigger severe weather concern is centered around Saturday. The deepening low tomorrow will be more mature so confidence in severe weather in the north-central plains is higher. The area of concern is in northwest SD, north into ND and west into Montana.

Beyond that, temperatures will be on the rise. Friday's highs will be in the 80s with the weekend seeing highs reach the 80s to 90s. Even warmer weather is likely next week. Stay tuned for the latest.

DISCUSSION

(This Evening Through Thursday) Issued at 1235 PM MDT Thu Jun 25 2026

Vis/IR satellite imagery depicts clearing skies over our northeastern WY counties with line of storms pushing eastward across northern WY. Further east of this line, isolated convection has begun to develop over the Bighorns. Most recent CAMs show the line of storms pushing eastward into the far western reaches of our CWA by mid- afternoon. Forecast DCAPE of 900-1000 J/kg and somewhat steep 700mb lapse rates of 6-7 C/km will support isolated severe wind and hail potential, mainly across Campbell County. This line should weaken as it moves eastward into SD and while a stronger storm or two can't be ruled out, widespread severe weather is not expected.

Longwave trough pushes into the western US on Friday with zonal westerly flow over our neck of the woods transitioning to southwest flow. Southeast sfc flow will bring warm, moist air into the region with ML CAPE values rising to 1000 to 2000 J/kg across the western half of our CWA by the late afternoon/evening hours. However slight height rises and warm 700 mb temps will likely keep the severe threat conditional for Friday. CAMs show some convection developing over northeastern WY Friday afternoon and moving into western SD by the evening hours. Inverted-V profiles with steep low level lapse rates and high LCLs indicate high based storms with a severe gust threat.

Severe potential continues on Saturday as a shortwave and attendant lee sfc trof/low moves through the region. Current thinking is that as the sfc trof deepens over western SD, axis of 2500-4000 J/kg SB CAPE will develop in the warm sector. Meanwhile, bulk shear of around 30 to 45kt will support rotating updrafts and organized convection. The main question is where the strongest instability and shear will set up, which current model runs are still not in great consensus about. So far, the highest confidence for where severe weather may occur on Saturday is across northwestern SD towards central SD. Confidence decreases closer to the Black Hills and southwestern SD into northeastern WY. Initial convection may start out as discrete supercells with all hazards possible before growing into an MCS with wind and hail becoming the main threats.

Unsettled southwest flow continues over the CWA through Sunday as the western US trof deepens. This will result in chances for storms later Sunday into Monday. Additionally, temperatures will continue to warm through this weekend with highs in the 80s to 90s by Saturday and Sunday. After a slight cool down on Monday, ensemble guidance is signaling much warmer conditions for later next week as a ridge builds over the eastern and central US.

AVIATION

(For the 06Z TAFS Through 06Z Friday Evening) Issued At 1043 PM MDT Thu Jun 25 2026

Low clouds will be lingering around the southern Black Hills and east into tonight, burning off a few hours after sunrise. Except MVFR conditions at KRAP during this time. Once the clouds dissipate, VFR conditions are expected for Friday afternoon before potential shower and thunderstorms impacts in northeastern WY around 22Z and western SD a few hours later. Dry conditions beneath any thunderstorms will support strong and erratic wind gusts.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.